A stage being constructed for a concert by pop star Madonna collapsed, killing one worker and injuring seven others, police in the southern French city of Marseille said.

The Sunday concert at the Velodrome stadium, home to the Olympique Marseille soccer team, was immediately cancelled.

"The roof of the stage caved in. It was only two-thirds finished," Maurice Di Nocera, a Marseille city official, told France Info radio.

The dead worker was a 53-year-old Frenchman. Two of the injured, an American and a British citizen, were in a serious condition, Interior Minister Brice Hortefeux said.

Marseille city hall said all the victims worked for a company called Live Nation, which was preparing the show.

Madonna was in Udine, Italy, at the time of the accident.

"I am devastated to have just received this tragic news," the singer said in a statement published on her website.

"My prayers go out to those who were injured and their families along with my deepest sympathy to all those affected by this heartbreaking news," she added.

The Marseille concert was part of Madonna's world "Sticky and Sweet" tour.